Thermostatic control for hotwater heaters and the like



Feb. 12, 1952 J. H. LESLIE, IL, ET AL 2,585,

THERMOSTATIC CONTROL FOR HOT-WATER HEATERS AND THE LIKE! Filed Dec. 22,1945 5 Sheets-Sheet l Feb- 12, 19 2 J. H. LESLIE, 11., ETAL 2,5

THERMOSTATIC CONTROL FOR HOT-WATER HEATERS AND THE-LIKE Filed Dec. 22,1945 5 Sheets-Sheet 2 F b. 12, 1952 J. H. LESLIE, IL, ETAL THERMOSTATICCONTROL FOR HOT-WATER HEATERS AND THE LIKE Filed Dec. 22, 1945 5Sheets-Sheet 3 Patented Feb. 12, 1952 THERMOSTATIC CONTROL FOR HOT-WATER HEATERS AND THE LIKE John H. Leslie, 11, and William A. Marshall,.Ir.,

assignorsto Stewart- Warner Corporation, Chicago, 111., a corpora-Indianapolis, Ind.,

tion of Virginia Application December 22, 1945, Serial No. 636,743

1 Claim. 1

The present invention relates to water heaters and more specifically toa type of small liquidfrom a conventional hot water heater locatedwithin the drivers compartment of an automobile, it will be appreciatedthatthe invention relates more generally to hot water-heaters and alsoto similar heaters intended for heating liquids other than water.

Ordinary hot water heaters used in automobiles comprise a heat exchangerwhich receives hot water from the engine cylinder block on the inletside and which discharges the water from the heat exchanger back to thecylinder block. Water heated by the engine is therefore passed throughthe heat exchanger and a portion of the heat is removed therefrom by anelectric fan which passes air to be heated through the heat exchanger.One disadvantage of such a heating system is that no heating effect isproduced until the water in the engine cooling system rises somesubstantial amount.

The heater of the present invention is inserted in the hot water linewhich leads from the engine block to the hot water heater ofconventional design in such manner that all of the water passing fromthe engine to the conventional hot water heater must pass through thedevice of the present invention. The present device has a combustionchamber in which gasoline is burned at a comparatively high rate so thatheat can be transferred to water passing through the device of thepresent invention at a rate of approximately 50,000 B. t. u. an hour. Itis apparent, therefore, that water passing to the conventional hot waterheater is raised to a substantial temperature within a matter of a fewseconds after the device of the present invention is started.

It 'is the principal object of the present invention to provide animproved hot water heater of the above type which has a novel controlsystem for the regulation of the flow of fuel to the heater.

An additional object of the present invention is to provide a novel hotwater heater control which is operative to shut off the flow of fuel tothe heater whenever the water in the heater jacket rises to somepredetermined level, and which also acts as a safety device to turn oilill the heater in the event that water is not present in the heaterjacket in suilicient quantity for safe operation.

A further object of the present invention is to provide a novel hotwater heater having an improved control system which can be supplied atcomparatively low cost, is safe and sure in operation and requiressubstantially no maintenance in service.

Other objects and advantages will become apparent from the followingdescription of a preferred embodiment of my invention which isillustrated in the accompanying drawings.

In the drawings, in which similar characters of reference refer tosimilar parts throughout the several views:

Figure l is a top view of a hot water heater embodying the presentinvention with a portion of the liquid connection broken away to Showinterior structure;

Fig. 2. is a longitudinal sectional view of the heater illustrated inFig. 1 and may be considered as taken substantially along the line 22 ofFig. 1 in the direction indicated by the arrows;

Fig. 3 is an irregular transverse sectional view which may be consideredas taken substantially along the line 3-3 in the direction indicated bythe arrows of Fig.2; and

Fig. 4 is an electrical circuit diagram illustrating the control circuitfor the heater illustrated in the foregoing figures.

The heater indicated generally by the numeral I0 comprises a conicalcombustion chamber I 2 located within a cylindrical inner shell I withthe large end of the burner toward one end of the shell while thesmaller end thereof empties into the generally cylindrical space. Theshell 14 togther with a concentric larger sleeve I6 forms an inner waterjacket [8 which is closed at its ends by means of annular flanged rings20 and 22 soldered or brazed to the cylindrical sleeves l4 and [6. Thisinner water jacket I8 is surrounded by an outer water jacket 24 spacedtherefrom and comprised of a pair of generally cylindrical concentricspaced sleeves 2G and 28 At the bottom of the heater the inner of thesesleeves 2B is formed to provide a depressed area 30 which is broughtinto contact with the sleeve 16, this depressed area being punched toprovide a circular opening through which a portion of the metal of thesleeve I6 is extruded and rolled over to form a circular seam 32 aroundan opening which provides communication between the outer water jacket24 and the inner water jacket 3 II. To prevent leakage. this scam issoldered. At the bottom of the heater this opening or passage isindicated by the numeral 34 while at the top 01' the heater a similarlyformed passage is indicated by the numeral 38.

At the end of the heater opposite the burner I2, the outer water jacketis extended to form a reentrant portion by means of inner and outercones 38 and 40, respectively. As will be seen in Fig. 2, the inner cone38 is rolled over near its outer edge to provide a cylindrical portion42 which is soldered to the end of the sleeve 28. Similarly, the outercone 40 is rolled over and soldered to the end of the outer shell 28. Inorder to space the cones 38 and 40 a proper distance apart to provide awater jacket, these cones near their centers are provided with mutuallyabutting extrusions 44 and 48 which prevent the cones from approachingeach other more than a predetermined distance. Similarly, extrusions 48are provided in the outer shell 28 so as to space this shell from thenext adjacent shell 26.

At the burner end of the heater, a flanged ring 9 acts as a cap toprovide a closure for the end of the outer water jacket space 24 while astepped cup closes the space between the shell 28 and a cylindricalbailie 52 which acts to prevent products of combustion from flowingdirectly from the burner to the exhaust connection. The central portionof the cup 50 also acts as the closure for the back of the burner I2.

Near the bottom of the burner I2 the closure cup 50 is provided with apocket 54 into which liquid fuel flows by way of a tube 56 and fitting58. This pocket also is equipped to receive an igniter 60 of the hotwire type energized through an igniter wire 62. The igniter whenenergized acts to vaporize gasoline or other liquid fuel in the pocket54 and subsequently ignites the combustible vapor to start the fire inthe combustion chamber I2. After the fire has been started, the ignitermay be de-energized. Air for combustion is introduced through a tube 84which enters the combustion chamber tangentially at the top thereof. Theopposite end of this tube extends through baflie 52 and the heatershells 26 and 28 and outside the heater case is bent at right angles andis connected to the outlet of a centrifugal blower '68. This blower isdriven by a small electric motor 88 which is secured to the heater caseby means of a suitable bracket I0.

When the burner is operating, products of combustion flow from theburner I2 into the cylindrical space adjacent thereto and heat the innersleeve I4. Heat is therefore transferred to the water within the jacketIS. The hot products of combustion also flow against the conical surface38 and heat the water jacketed between this cone and the outer cone 40.After transferring a considerable portion of heat to the water as aboveindicated, the products of combustion flow around the end of the ringand between the shells I6 and 26, thereby transferring more heat to thewater within the jacket I8 and to the water within the outer jacket 24.At the burner end of the heater the products of combustion are collectedwithin the annular plenum chamber 12 and pass outwardly through anexhaust spud I4 which communicates with the plenum chamber I2 through anopening I6 in the shells 28 and 28, this opening being sealed againstwater leakage in the same manner as the openings 34 and 36.

Water is introduced into the outer jacket space 24 by means of a tubularfitting I8 rolled over the edge of an opening in the shell 28, thefitting then being soldered in place to insure against leakage. Waterflowing into the heater, therefore, directly enters the outer jacket 24and passes into the jacket I8 by way of the opening 38. At the top ofthe heater the outer water jacket 24 is provided with an outlet openingdirectly opposite the passage 38 which communicates between the innerand outer jackets. The metal around the opening 80 is extruded outwardlyand rolled over to form a connection with an elbow fitting 82, the jointbeing sealed with solder to prevent leakage. Elbow fitting 82 isconnected at its outlet by means of a rubber sleeve 84 with an adapter88 which in turn is connected to a rubber hose 88 which carries the hotwater away from the heater. In a conventional installation the hose 88will be connected to a conventional hot water heater located within thedriver's compartment. In order to control the flow of liquid through thesystem, the hose connection 84 contains a liquid thermostat 90 which maybe of conventional type and which opens at a predetermined temperature,as an example, degrees R, so as to permit water to flow through thesystem as long as the water temperature is above this predeterminedlevel and to inhibit flow through the system until this level has beenreached.

The top of the elbow fitting 82 in a position directly opposite thepassages 80 and 36 is provided with a threaded boss 92 to receive thehead 94 of a thermostatic bulb 96 which is connected by means of acapillary tube 98 with a pressure responsive control switch I00.Whenever,-with this system, the temperature of the bulb 98 rises, thevapor pressure therein will rise, thus raising the pressure in the tube98 and in the pressure responsive switch I00. The bulb 98 contains aquantity of fluid with proper vapor pressure characteristics to operatewithin the temperature range desired. Preferably air is exhausted fromthe bulb 98 before it is sealed and the liquid filling is so chosen thatthroughout the temperature range the pressure within the bulb issubatmospheric. As the temperature rises, the vapor pressure of theliquid increases and operates the switch I00 at a, higher but stillsubatmospheric pressure. For the purpose of controlling a heater of thetype indicated, we have found that ethyl alcohol has good vapor pressurecharacteristics and is satisfactory for use in the control bulb 96 andassociated mechanism although other liquids may be used if desired.

Inasmuch as the specific switch I00 forms the subject matter of aseparate application, no further description need be given as to thedetails of its construction. For the present purpose, it is sufficientto indicate that the tube 98 is connected to a bellows I02 which forms aportion of the switch mechanism I00 and this bellows upon beingelongated operates in sequence three separate switches I04, I08 and I08.

As indicated in Fig. 4, all three of these switches are closed atambient temperature and are so arranged that as the bellows I02elongates switch I04 opens at a comparatively low temperature anddisconnects the igniter 60 from the automobile battery IIO, the batterybeing connected to the switches I04, I06 and I08 by way of a main heaterswitch II2. At a higher temperature, switch I06 is opened, therebyde-energizing an electromagnetic restricting valve II4 located in thefuel line 56 leading to the heater I0. Valve H4 is of the type whichpermits a full flow of fuel therethrough when energized, but whichpermits a low rate of flow when de-energized.

Closure of this valve, therefore, acts to shift the heater from highheat operation to low heat operation.

At a still higher temperature the switch I08 is opened, therebyde-energizing a second magnetic valve II6 which is'of the on-oil type.The de-energization of this valve, therefore, interrupts the flow offuel from the fuel pump II8 to the heater I0, thereby turning off theheater. Under normal operating conditions it is desirable to shift theheater from high heat operation to low heat operation as the temperatureof the water rises slightly above that at which the liquid thermostat 90opens. When the water temperature rises somewhat thereabove, the heateris turned oil, since such temperature conditions of the water indicatethat the engine is supplying enough heat so that it alone can maintain acomfortable level within the driver's compartment. Because of thepossibility that the heater may be started without suflicient waterbeing present in the water jackets, it is desirable to have some type ofsafety device for turning off the heater in the event that the jacketmetal temperatures exceed some predetermined level. In order toaccomplish this objective, the bulb 96 of the thermostat is slippedlongitudinally into a deep drawn cup I in such manner that good metal tometal contact is obtained between the cup I20 and the bulb 96. This maybe accomplished by slotting the cup I20 longitudinally and thenproviding a clamping band I22 which is tightened after the bulb is inplace so as to squeeze the side walls of the cup against the surface ofthe bulb. Preferably the cup I20 should be formed of a metal having highthermal conductivity, such as brass or copper, for instance, and thelower end of the cup is welded or brazed or otherwise suitably attached,as indicated at I24, to the surface of the inner shell I4. The cup I20is also provided with a plurality of perforations I26 in the side wallsthereof in a position beneath the end of the bulb 96 and above the pointof attachment of the cup I20 to the inner shell I4. These perforationspermit water from the Jacket to enter the space within the cup I20 belowthe bulb 96.

We have found that with a device constructed as above indicated theliquid within the water jacket will circulate through the openings I20and into the space beneath the bulb 96 and will flow in contact with theportion of the bulb above the cup I20. It will act, therefore, totransfer heat away from the cup I20 in such manner that the temperatureof the bulb 96 will always be at substantially the water temperature, solong as water is present within the jacket. On the other hand, if theheater is operating and water is absent from the jacket, heat will beconducted from the shell I4 to the cup I20 and up the side wall of thecup to the bulb 96 so as quickly to raise the temperature of the bulb.The result is that whenever the inner shell I4 is excessively heatedbecause of the absence of water from the system, this dangerouscondition will quickly result in heat being conducted to the temperatureresponsive bulb 96 so as to raise the temperature of the liquid thereinsufflciently to elevate the vapor pressure to the point where thebellows I02 expands and opens all three of the switches I04, I 08 andI06, thereby turning oil the heater. It is apparent, therefore, that bythe simple expedient of arranging the bulb 96 in good heat conductingrelation with the tube I 20 and by connecting this tube to the innershell I4 and further by forming the tube or cup I20 of a metal having ahigh rate of thermal conductivity, the bulb l8 and control switchassociated therewith act in a normal manner to sense the watertemperature when water is present in the system and also serve to sensethe metal temperature, so as quickly to shut off the heater in the eventthat combustion is started without sufllcient water being present in thesystem.

Inasmuch as the liquid filling for the bulb is so chosen that its vaporpressure is below atmospheric at normal control temperatures, therebypermitting all three of the switches I04, I06 and I09 to be openedbefore the pressure within the bulb 96, tube 98 and bellows I02 reachesatmospheric, the system is inherently safe, or as it is commonlyexpressed "fails safe. In other words, if any portion of the vaporsystem should 'leak, the subatmospheric .pressure therein will cause airto leak into the system, thereby permitting the bellows I02 to elongateso as to turn off the heater. The heater, of course, remains off untilthe defect has been repaired.

From the above it will be seen that by a simple mechanical expedientwhich adds very little to the cost of the heater, we have caused thewater temperature control system to do double duty by also serving as asafety control to turn 01! the heater in the event that it is startedwithout sufficient water being present in the Jackets.

Having described our invention, what we claim as new and useful anddesire to secure by Letters Patent of the United States is:

In the combination which includes a water heater or the like having ametal surface heated on one side and cooled on the other side by waterto be heated and a thermally responsive element immersed in water forregulating the heater according to the water temperature, theimprovement in the thermally responsive element which comprises athermostatic bulb, a generally tubular metallic element of relativelyhigh thermal conductivity to support said bulb in the upper region ofthe water space in said heater in spaced relation to said surface, saidbulb being telescopically received in and closely embraced by one end ofsaid tubular element and the opposite end of the latter being secureddirectly to said surface to form a metallic heat conducting path forrapidly conducting heat from said surface to said bulb whenever thelevel of the water falls below said opposite end, the wall of saidtubular element having openings therethrough between said bulb and saidopposite end to afford free passage of water between the inside andoutside of said tubular element.

JOHN H. LEsLm, Ir.

WILLIAM A. Jn.

REFERENCES crrnn The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Date

